/Engine/Source/Editor/GraphEditor/Public/SGraphActionMenu.h
Delegate that can be used to create a custom "expander" widget for a particular row
typedef TBaseDelegate_OneParam< [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SExpanderArrow](API\Runtime\Slate\Widgets\Views\SExpanderArrow) >, [FCustomExpanderData](API\Editor\GraphEditor\FCustomExpanderData) const & > FOnCreateCustomRowExpander